Hydraulic fracturing can increase the rate of production of oil and gas from low-permeability reservoirs. Hydraulic fracturing increases the permeability of reservoir rocks by opening channels through which oil and gas can travel to recovery wells. During hydraulic fracturing, a fluid is pumped through a wellbore under high pressure into a subterranean reservoir where it splits or fractures the reservoir rock. A proppant, like sand, is often added to the pumped fluid and carried in suspension into the newly formed fractures. When pumping ceases, the fractures partially close on the proppant, leaving open channels for oil and gas to flow to a recovery well that is usually the well through which the fracture fluid was pumped.
High-pressure pumps are used to complete hydraulic fracturing procedures or “frac jobs.” These pumps have “fluid ends” within which a number of reciprocating plungers pressurize a fracture fluid. Suction and discharge valves control fluid flow to, and from, the plungers. Within these valves are pistons that normally press against valve seats to selectively stop the flow of fluid. When the pressure within a suction valve is reduced below a predetermined threshold, its piston will move away from its seat thereby permitting fluid to enter a fluid end. Similarly, when the pressure within a discharge valve is raised above a predetermined threshold, its piston will move away from its seat thereby permitting fluid to exit a fluid end.
To reduce leaks around valve seats and maximize pumping efficiencies, the pistons found in suction and discharge valves are typically equipped with sealing elements. These sealing elements or inserts are typically rings formed of a resilient material. The rings are fitted into grooves in the pistons that are positioned to facilitate contact with valve seats. Typical designs of sealing elements have permitted them to move about in their retaining grooves after installation, permitting them to wear excessively in the presence of abrasive proppants and other materials carried by fracture fluids. Thus, the known sealing elements required frequent replacement
Pump manufacturers have made few provisions in their pumps for replacing worn parts in suction and discharge valves. Sealing elements are located deep within the fluid end of a pump that is held together by a large number of heavy, threaded fasteners. To access the worn sealing elements, the fluid end frequently required substantial disassembly. Although manufacturers provide strong and robust pumps, disassembly of pumps in the field is especially time-consuming and difficult to perform. Increasing the longevity of the sealing elements found in suction and discharge valves can, therefore, provide substantial cost savings to an oilfield operator.